Hi Moreno,
I faced exactly the same issue as you did. I had two ABAP-stacks "C11" on Hosts "sapc11"
But I was lucky, as I had some (additional) virtual hostnames for the Systems.
For ABAP-stacks, check out DEFAULT.PFL. Usually, there are entries for SAPGLOBALHOST and SAPDBHOST (for a central System, they are the same, here: "sapc11").
I solved my issue in adding the Parameter SLDSYSTEMHOME and set the value to a virtual hostname. This value is transferred regularly via RZ70, you will see a new entry in SLD.
Hope this helps.
Regards,
Dirk